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-rw-r--r--kernel/fork.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index a28d11e..2c78068 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1003,9 +1003,6 @@ static task_t *copy_process(unsigned long clone_flags,
p->pdeath_signal = 0;
p->exit_state = 0;
- /* Perform scheduler related setup */
- sched_fork(p);
-
/*
* Ok, make it visible to the rest of the system.
* We dont wake it up yet.
@@ -1014,18 +1011,24 @@ static task_t *copy_process(unsigned long clone_flags,
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
+ /* Perform scheduler related setup. Assign this task to a CPU. */
+ sched_fork(p, clone_flags);
+
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
/*
- * The task hasn't been attached yet, so cpus_allowed mask cannot
- * have changed. The cpus_allowed mask of the parent may have
- * changed after it was copied first time, and it may then move to
- * another CPU - so we re-copy it here and set the child's CPU to
- * the parent's CPU. This avoids alot of nasty races.
+ * The task hasn't been attached yet, so its cpus_allowed mask will
+ * not be changed, nor will its assigned CPU.
+ *
+ * The cpus_allowed mask of the parent may have changed after it was
+ * copied first time - so re-copy it here, then check the child's CPU
+ * to ensure it is on a valid CPU (and if not, just force it back to
+ * parent's CPU). This avoids alot of nasty races.
*/
p->cpus_allowed = current->cpus_allowed;
- set_task_cpu(p, smp_processor_id());
+ if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed)))
+ set_task_cpu(p, smp_processor_id());
/*
* Check for pending SIGKILL! The new thread should not be allowed
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